Adaptation and Response of Bifidobacterium animalis subsp. lactis to Bile: a Proteomic and Physiological Approach

Abstract

Bile salts are natural detergents that facilitate the digestion and absorption of the hydrophobic components of the diet. However, their amphiphilic nature makes them very inhibitory for bacteria and strongly influences bacterial survival in the gastrointestinal tract. Adaptation to and tolerance of bile stress is therefore crucial for the persistence of bacteria in the human colonic niche. Bifidobacterium animalis subsp. lactis, a probiotic bacterium with documented health benefits, is applied largely in fermented dairy products. In this study, the effect of bile salts on proteomes of B. animalis subsp. lactis IPLA 4549 and its bile-resistant derivative B. animalis subsp. lactis 4549dOx was analyzed, leading to the identification of proteins which may represent the targets of bile salt response and adaptation in B. animalis subsp. lactis. The comparison of the wild-type and the bile-resistant strain responses allowed us to hypothesize about the resistance mechanisms acquired by the derivative resistant strain and about the bile salt response in B. animalis subsp. lactis. In addition, significant differences in the levels of metabolic end products of the bifid shunt and in the redox status of the cells were also detected, which correlate with some differences observed between the proteomes. These results indicate that adaptation and response to bile in B. animalis subsp. lactis involve several physiological mechanisms that are jointly dedicated to reduce the deleterious impact of bile on the cell's physiology.

Genetic and Physiological Responses of Bifidobacterium animalis subsp. lactis to Hydrogen Peroxide Stress

“…Schell et al (26) suggested that these enzymes might be one of the primary defense mechanisms against oxidative stress in bifidobacteria, and other research has shown upregulation of thioredoxin, thioredoxin reductase, and peroxiredoxin genes in response to oxygen stress (27,28). Interestingly, exposure to bile can also produce an oxidative stress response via generation of oxygen free radicals (29), and Sanchez et al (30) found that bile stress induced a thioredoxindependent thiol peroxidase in B. animalis subsp. lactis.…”

Catabolism of Glucose and Lactose in Bifidobacterium animalis subsp. lactis, Studied by 13 C Nuclear Magnetic Resonance

“…The bifid shunt has been partially characterized in terms of enzymatic activities (9,19), and the labeling pattern of end products derived from Glc metabolism in Bifidobacterium bifidum ATCC 29521 was investigated by 13 C nuclear magnetic resonance (NMR) using as metabolic tracers Glc specifically labeled on carbons 1 and 3 (20). In vivo 13 C NMR is a noninvasive technique that allows the monitoring, online and in real time, of the concentrations of end products and intracellular metabolites, as well as the rates of substrate consumption, during the metabolism of labeled substrate by nongrowing cells under controlled temperature and atmosphere conditions (21). This technique has facilitated the study of different pathways in various species, such as Lactococcus lactis, Staphylococcus aureus, and Escherichia coli (22)(23)(24).…”

“…The fructose 6-phosphate phosphoketolase (Xfp) is the characteristic enzyme of this path, which holds a dual substrate specificity, acting on fructose 6-phosphate or xylulose 5-phosphate to produce aldose phosphate, acetyl phosphate, and H 2 O (10-12). Glyceraldehyde 3-phosphate and acetyl phosphate are further metabolized to produce the end metabolites of the pathway, with acetate, lactate, and ethanol being the most abundant (13).…”

HspR Mutations Are Naturally Selected in Bifidobacterium longum When Successive Heat Shock Treatments Are Applied

“…In order to obtain bacterial strains with better resistance to stress, the selection of natural variants was previously applied to bifidobacteria, e.g., for resistance to cholate (20), acid (9,29), or bile (30). With the current work, we applied a similar approach that may be seen as an accelerated evolution of a bacterial strain: sequential selection of naturally occurring mutants showing an adaptation to specific physiological conditions.…”

“…However, even in such a species, variations in stress tolerance have been documented (19). Robust stress-resistant mutants arise, sometimes spontaneously (9,20,29,30). Specific stress-tolerant mutants might thus be obtained by natural selection.…”